Objective: To identify the socio-demographic antecedents and pregnancy-related history of infants with abnormal head sizes in a developing country. Materials and Methods: An observational study of mother-infant pairs attending routine immunization clinics in an inner-city community in Lagos, Nigeria. Age and gender-specific head circumference was determined with the current Child Growth Standards of the World Health Organization (WHO). Factors independently associated with any abnormal head size (z-score 2SD), based on the adjusted odds ratio (OR) and 95% confidence interval (CI), were explored with multiple logistic regression analyses. Results: Of the 5731 mothers studied, 730 (12.7%) had an offspring with an abnormal head size. In the final regression model, teenage mothers (OR:1.86; CI:1.26 - 2.75), mothers with primary or no education (OR:1.65; P = 0.007), multiple pregnancies (OR:3.88; CI:2.53 - 5.95), and delivery in either private hospitals (OR:1.54; CI:1.22 - 1.95) or residential homes (OR:1.50; CI:1.05 - 2.14), compared to government hospitals, were significantly more likely to have offsprings with abnormal head sizes. Conclusions: Community-oriented public health education, targeting prospective mothers with multiple pregnancies, teenage girls, and women with little or no formal education on the potential risk of delivery outside public hospitals, may curtail the burden of abnormal head size of their offspring and reduce the pressure on the already overstretched rehabilitation services in resource-poor countries.